Unfortunately, I don’t remember the source so we may need to go digging. But I recall reading that something like 1/3 of all bugs are related to memory safety. And those bugs translate to things like buffer overflow and privilege escalation attacks.
The proclaimed advantage is that by making the entirety of Rust memory safe, that entire class of bugs simply won’t exist for projects written in Rust. When they do happen, the bugs will be addressed by the language rather than many thousands of downstream projects. It should be an enormous gain in development performance for the world.
I think the idea makes sense. Time will tell us how well that works.